Ottobah Cugoano was born about the year 1757, on the coast of what is today Ghana. When he was about 13, he was kidnapped and put on board a ship that carried him to Grenada. After nine or ten months in the slave gang there, and a further year on different West Indian islands, he was brought to England by his owner at the end of 1772 and set free. Advised to get himself baptized in order not to be sold into slavery again, he took the name John Steuart. Later, he entered the service of Richard Cosway, principal painter to the Prince of Wales, and before long emerged as one of the leaders and spokesmen of London's black community.

In 1786, Cugoano played a key part in the rescue of Henry Demane, a black man who had been kidnapped and was being shipped out to the West Indies. Cugoano and another community leader, William Green, reported the kidnapping to the white abolitionist Granville Sharp, who got a writ of habeas corpus, and rescued Demane at the last minute, just as the ship was weighing anchor.

The following year Cugoano published a powerful contribution to the campaign for the abolition of the slave trade, his Thoughts and sentiments on the evil and wicked traffic of the slavery and commerce of the human species. It is believed that Olaudah Equiano collaborated with him on this work. In it, Cugoano and his collaborator destroyed the arguments in defence of slavery; that black slaves in the Caribbean were better off than the European poor; that slavery had divine sanction; that Africans were, by nature and complexion, peculiarly suited to slavery. On the contrary, the slaves were bought and sold and dealt with as their capricious owners saw fit, 'even torturing and tearing them to pieces, and wearing them out with hard labour, hunger and oppression'.

Cugoano went further than just denouncing slavery. He was the first writer in English to declare that enslaved blacks had not only the moral right, but the moral duty to resist:

If any man should buy another man, and compel him to his service and slavery without any agreement of that man to serve him, the enslaver is a robber and a defrauder of that man every day. Wherefore it is as much the duty of a man who is robbed in that manner to get out of the hands of his enslaver, as it is for any hones community of men to get out of the hands of rogues and villains.

Cugoano sent copies of his Thoughts and sentiments to King George III, the Prince of Wales and the politician Edmund Burke; however, all remained supporters of the slave trade. In a postscript to a shorter version of his Thoughts, Cugoano announced his intention of opening a school, mainly for 'all such of his complexion as are desirous of being acquainted with the knowledge of the Christian religion and the laws of civilisation'. It is not known whether he succeeded in opening the school, nor what became of him after 1791. He was the first published African critic of the transatlantic slave trade, and the first African to demand publicly the total abolition of the trade and the freeing of the slaves - a position which scarcely any white abolitionist had taken by 1787.